Fluid sample bags are used in a variety of applications to obtain gaseous and liquid fluid samples, for example in testing automotive exhaust gases. Typically, a fluid sample bag comprises a flexible bag which is sealed and impermeable to prevent leakage and loss of the sample from the bag and protect against contamination of the sample. It is particularly important that the bags be impermeable to gases where gaseous fluid samples are taken. Typically, the fluid sample bag includes a fitting to introduce a measured quantity sample into the bag and then to remove the sample from the bag.
The sample is removed for testing to determine whether certain constituents are present within the sample and to quantify the presence of the constituents, typically contaminants in the case of automotive exhaust gases. In many cases the constituents are present in very small quantities, e.g., parts per million. Therefore, if the measured sample is not completely removed from the bag, constituents may be left in the bag and remain undetected. In addition, if it is desired to reuse the bag repeatedly, a given sample from the bag must be completely evacuated so that it does not contaminate a subsequent sample.
A typical prior art bag B, as shown in FIGS. 1 and 1A, is assembled with a fitting F and flexible tubing T inside the bag. The bag is sold assembled with the fitting F and tubing T. Tubing T is intended to serve as a manifold to introduce and to extract the sample.
However, as shown in FIGS. 1 and 1A, prior art bags B having flexible tubing T may form pockets P of entrapped gas when the bag is evacuated. This occurs because the top and bottom of the bag B can collapse onto itself, sealing off pockets P during evacuation.
Objects, features and advantages of this invention are to provide a fluid sample bag which, as contrasted to prior art bags, is reliable and operates effectively to provide accurate and repeatable fluid sampling. According to the present invention, the prior art tubing inside the bag is replaced with a spacing element that enhances fluid flow, facilitates drawing a sample from the bag, and restricts collapsing of the bag onto itself and thus prevents the formation of isolated pockets of fluid sample and insures substantially complete evacuation of a sample from the bag.
These and other advantages and features of the invention will be apparent from the following detailed description and claims.